Research And Design Of 2W Broadband Power Amplifier Based On GaAs Technology

With the rapid development of wireless communication technology, the increasing number of the users and the limited resources of spectrum require higher spectrum efficiency and higher date rate, people now demand higher spectrum efficiency and higher data rate of current communication system. Compared with the traditional power amplifier, Broadband RF Power Amplifier boasts a series of advantages such as bigger bandwidth, wider dynamic range, higher efficiency, better temperature stability and so on. The research and design of RF PA is of great significance due to the important role that RF PA plays in the military and personal communication systems as well as the fact that China has not yet reached the international cutting-edge level in this field.RF power amplifier always required to output a certain output power in a given frequency range, while the terminal and base stations require enough efficiency and high linearity from PA. RF power amplifier is always working in the condition of large signal, As a result, the device and circuit design methods used are different from those of the small signal models, making the design of the power amplifier even more difficult.Based on marker demands and research needs, the GaAs HBT technology is adopted and a high gain, high output power and high efficiency PA is realized with a two-stage amplifier structure. This paper analyzes key problems in PA design, and then put forward effective solutions. The paper studies the model of active device, analyzes the amplifier’s gain and stability using the parameter S. It also elaborates on the impedance matching network and bias network implement method and summarizes several major RF PA design methods. Some effective solutions are proposed in the paper. The adaptive linear bias circuit is designed for providing bias to the transistors, at the meantime, it reduces the temperature sensitivity of the circuit effectively. The RC parallel network inserted in base and collector eliminates potential HBT tube unstable factors, thus improving the stability of the circuit. This paper designed a two stage RF power amplifier, the first stage using conjugate matching for maximum gain, the second stage design in accordance with the principle of power match in order to achieve maximum power output. Ultimately, the parasitic effect is considered sufficiently the layout designing and PCB testing. At last, this paper analyzes and summarizes deficiency of the circuit.